The present invention pertains to a clutch plate for a friction clutch.
The invention relates more particularly to such a clutch plate comprising a friction disc and a hub mounted for relative angular displacement within a predetermined range. The friction disc and the hub are coupled together by first and second stage torsion damping means. The first stage torsion damping means being lower rated or lighter than the second stage torsion damping means. Each stage torsion damping means has a radial flange, two guide washers on axially opposite sides of the associated flange and resilient means circumferentially interposed between the flange and the associated guide washers. The first stage damping means is operative between the hub and the second stage damping means and the friction disc is fixed to one of the guide washers of the second stage damping means.
The second stage damping means which is higher rated or stiffer and which may have more than one stage including springs of different spring stiffenesses has the main damping function during normal operation when the torque transmitted in either direction by the clutch plate has a substantial value. The second stage damping means has a filtering function in the transmission of torque particularly when it equips a motor vehicle.
The second stage damping means, despite its efficacy in normal operating conditions, is found to be insufficient to efficiently absorb vibrations when the torque transmitted by the friction disc is very low or nil, such as found when a motor vehicle idles; in this mode of operation the second stage damping means is incapable of preventing the noises known as dead point or idling noises from developing. That is the reason why the first stage damping means operates as a pre-damper specially adapted for damping vibrations and noises in particular operating conditions in which the torque transmitted is very low, notably when the vehicle is idling.
The present invention relates more particularly to a clutch plate in which the friction disc of the first stage damping means is fixed for rotation with the hub and the first stage guide washers are fastened to the second stage damping means.
It will be readily understood that the simultaneous presence of two torsion damping means poses a problem of bulkiness which heretofore has not been resolved in a very satisfactory manner. In particular in known clutch plate designs the two torsion damping means are interleaved and various components are mutually interengaged which results in a complicated assembly and lowers the mechanical strength of the entire clutch plate.